This invention relates to a connector to be used in the production of optical fibre preforms for connecting a process steam and gas supply pipe rotatably to a silica tube to be formed into a preform, comprising a generally cylindrical body part provided with a through-going bore for the supply pipe, said bore comprising one or more annular expansions for a ring seal or ring seals sealing the supply pipe with respect to the body part.
When producing optical fibre preforms e.g. by MCVD process, in which the preform is grown inside a silica tube, it is necessary to provide a rotating connection between a pipe supplying process steam and gases, usually a pipe of stainless steel, and a silica tube to be formed into a preform. In a conventional arrangement the silica tube itself is first supported between the jaws of a so-called lathe rotating it. This takes place at a distance from the end of the silica tube. The process steam and gas supply pipe is attached to the end of the silica tube by means of a suitable connector allowing rotation. When the silica tube is supported in this way to the lathe rotating it, the rotating connection is subjected not only to rotary motion but also to axial and radial forces. For this reason, it has been necessary to provide the process steam and gas supply pipe with a bellows allowing these movements; on the other hand, the structure of the connector has been relatively complicated. Further, this way of supporting the silica tube means that the silica tube portion between the supporting jaws and the rotating connection cannot be utilized. Due to the high price of silica tube, this involves a substantial waste of material.